Hartmann and Shack–Hartmann Wavefront Sensors for Sub-nanometric Metrology

The recent development of third generation synchrotron radiation facilities has led to unprecedented progresse in X-ray applications such as microscopy and photolithography. To optimize performance in such research metrology tools with capabilities in the nanometre and even the sub-nanometre range, in order to characterize the surface figure errors of the optics used to focus or collimate the Xray beams, to align them on the beam lines and to perform diagnostics of the beam spatial profile. To answer these needs, Synchrotron Soleil and Imagine Optic have developed in partnership a Shack-Hartmann long trace profiler (SH-LTP) which performs the bidimensional surface figure measurement of X-ray mirrors with nanometer precision and an increased dynamic range compared to earlier instruments. The SH-LTP offers a more complete diagnostic for highly curved surfaces compared to standard LTPs. This partnership has also led to the development of X-ray Hartmann wavefront sensors to measure and control the spatial quality of X-ray beams. Compared to interferometric tools, these sensors have better flexibility and can be integrated into closed-loop adaptive optical systems.